Stopping two cars

Reflections wrote:

Lidar used by officers is invisible to the naked eye. You can however use nightvision to see them. I wonder why officers are not using nightvision to align the scopes???

I have used night vision to see the beam, very neat.

However, we are not trained/ qualified to align a scope. That must be done by the repair facility. What we do is ensure the unit is sighting properly, if the lidar fails the test, we place it out of service and send it for repair on the next Purolator truck.

Reflections wrote:

One thing though. I know that light travels at a constant speed in a vacuum. The atmosphere is not a vacuum. Dirt, smog.....all those airbourne particles can effect light. How would this be compensated for....? I know you're coming back to this 'bear so..... The further away a target is from the gun the more the "light" is going to slow down, simple physics. Is there a setting you have for "smoggy" days??? I know there are foul weather modes on different models. You cannot compensate for the unknown.

To my use, I start observing vehicles about 1km away (through scope) monitor, then hit the vehicle with lidar around 700m. Then again around 550m. Then my final hit is around 500m-100m. This allows a visual observation, confirmed targetting history. The lidar beam is very concentrated being this close and any smog would be less than minimal affect.

The addition of moisture in the air reduces the effective range of the lidar. ie light rain might reduce my first reading from 700m down to 500m. Snow is just horrible and a waste of my time using a lidar. It is not affecting the accuracy of the readings, just how far away a vehicle can be targetted.

And at the end of the day, I would rather use lidar.

At 100m

Lidar = 30cm beam width

Radar = 20 metres

There is absolutely never any doubt with lidar which vehicle is travelling what speed.

although......my best is at night, obtain a speed via radar/lidar, catch the vehicle and then pace it....then pull up beside and READ the drivers speedometer. (even more icing on the cake when the speedometer is digital )

New civic's are very nice for you......

Your style is very thorough. Next time you have the oppertunity on a smoggy day, light someone up from 1 km and keep the gun on them. If the speed decreases the closer they get closer then there is some effect.

I know you'll say they let they're foot off the gas but this would help prove the theory.

Reflections wrote:

New civic's are very nice for you......

Your style is very thorough. Next time you have the oppertunity on a smoggy day, light someone up from 1 km and keep the gun on them. If the speed decreases the closer they get closer then there is some effect.

I know you'll say they let they're foot off the gas but this would help prove the theory.

I'll give that a shot....pardon the pun!!

Just for giggles try it at night so they don't see you......

but won't know if it's smoggy

Is there a way of uploading pics on this forum? I have a few NURBS pics.

Imax wrote:

Is there a way of uploading pics on this forum? I have a few NURBS pics.

The best way is to store your pictures on any free file storing website.

www.Photobucket.com is free and provides 1 GB of free space.

Once you have uploaded your picture you can simply post your picture/image on this forum using bbcode:

[img]http://your-image-link-goes-here.com/image.jpg[/img]

thanks admin. It's working

NURBS setup. Two cars, one at 500m and one at 570m. Laser offset, 10m. The laser beam is a cone, 600m long and 1.8m at the base.

A perspecive:

Close up view:

When looking at the close up, its not too bad. Any beam hitting the side of car one wont be received by a lidar. But my NURBS model for car 1 and 2 arent realistic. They are two blocks, one on top of the other. Ive missed on important aspect, side view mirrors.

Good shots and they explain a lot. As much as they are not "perfect" they do demonstrate the problems facing officers. The third one's the best.....good job.

maybe a mod can spilt this over to the law enforcement tools area... somewhere above this....

*************************************

seeing that a lane is 3.75m wide a typical car is 2.6m wide.......beam width is still less than the width of the car.

At 500m beam is 1.5m wide. One at 570m...round it to even 1.8m for simplicity sake.

Your "blocks" are realistic for Jeeps and Hummers

You can still see that it is difficult to target the plate..... And like you said you can't see the beam even under alignment checks. The officer still does not know "exactly" where the beam is.......at a distance of 500 meters 1 degree is a lot, even 0.5 degrees of misalignment will cause this situation.

hwybear wrote:

maybe a mod can spilt this over to the law enforcement tools area... somewhere above this....

*************************************

seeing that a lane is 3.75m wide a typical car is 2.6m wide.......beam width is still less than the width of the car.

At 500m beam is 1.5m wide. One at 570m...round it to even 1.8m for simplicity sake.

Your "blocks" are realistic for Jeeps and Hummers

You are right, this thread is too long and discussion of lidars hijacked the thread. I shall have admin make me a mod for this section too and split it off.

Reflections wrote:

You can still see that it is difficult to target the plate..... And like you said you can't see the beam even under alignment checks. The officer still does not know "exactly" where the beam is.......at a distance of 500 meters 1 degree is a lot, even 0.5 degrees of misalignment will cause this situation.

I still do not see it when the beam is not relative to the distance. Nor are the size of vehicles. It to one perspective is construed, something like stats are!

OK try this one: The ideallogy of the designer is that the plate is the target. Ideally it is the first thing hit, being at the front of the car. What happens when the plate is not the first thing to be hit??????????? That info is locked up in the designers head and won't be released due to the fact that it can be used by the other companies.

The diagram still does not relate properly. I must be missing something in the description....all of a sudden we go from vehicles to a plate?

If it is to mean two targets at the same time....the lidar will not compute that and gives the operator an error.

Hi Bear:

Thats what Im wondering about. A lidar doesnt send a constant beam, but a series of pulses. Theres a microprocessor inside the lidar which tries to make sense of all signals received from all those pulses. Its going to try to get an average speed and throw out what could be noise. What if it locks onto car1s speed and thinks car2s speed is noise?

Sorry racer. I didnt mean to hijack my own post.

Imax wrote:

A lidar doesnt send a constant beam, but a series of pulses. Theres a microprocessor inside the lidar which tries to make sense of all signals received from all those pulses. Its going to try to get an average speed and throw out what could be noise. What if it locks onto car1s speed and thinks car2s speed is noise?

The lidar sends out more than 60 pulses per second. If 2 vehicles happen to be in the same beam, it will reject both and display an error message and NO speed reading. I am an operator of the unit, not an instructor, nor a scientist. If a dentist can use a lidar to fix my tooth or optometrist can fix my eyeball or military to guide bombs or reconstructionists to investigate traffic collisions, I think lidar is pretty precise.

hwybear wrote:

Imax wrote:

A lidar doesnt send a constant beam, but a series of pulses. Theres a microprocessor inside the lidar which tries to make sense of all signals received from all those pulses. Its going to try to get an average speed and throw out what could be noise. What if it locks onto car1s speed and thinks car2s speed is noise?

The lidar sends out more than 60 pulses per second. If 2 vehicles happen to be in the same beam, it will reject both and display an error message and NO speed reading. I am an operator of the unit, not an instructor, nor a scientist. If a dentist can use a lidar to fix my tooth or optometrist can fix my eyeball or military to guide bombs or reconstructionists to investigate traffic collisions, I think lidar is pretty precise.

When the beam is sent it hits the entire car. The gun will recieve the reflections from every point that is facing the gun. Thus, the amount of filtering done by the gun is extremely large. Now, when you target just the front plate, you are hitting the entire front end of the car. There are 3 good targets on the front of a vehicle, the plate and the 2 headlights. What you are saying about multiple targets doesn't add up.

I dont doubt that if two vehicles are in the same beam, experience says that a lidar will reject both and display an error message and no speed reading. I have no problems in seeing a lidar being able to get the speed of car1, but the angles for car2 are really tight. Im guessing the lidar for car2 would need to be moved from whats in the NURBS pics, possibly aiming at the closest headlight. Given the tight angle and beam divergence, I can only see two possibilities. The lidar is reading car1 speed or its reading an error message.

Imax wrote:

I have no problems in seeing a lidar being able to get the speed of car1, but the angles for car2 are really tight.

That is a better explanation of what I have been saying.......that IF the pictures were to scale (ie vehicles should be 2.6m wide) then there might be less chance a lidar could get #2.

Veh 1 width of 2.6m, 500m the beam is 1.5m wide...therefore the whole beam can be placed on the car...

Veh 2 width is 2.6m, 570m the beam width is 1.71m wide...therfore the whole beam can be placed on the car.

Now what we have is the angle from the lidar to the vehicles, on a angle, can it target the 2nd vehicle? There is also sideways movement within the lane (as it is 3.75m wide) that also is not taken into account. Which each vehicle could move 1.15m left or right. This could add up to another 2.30m of lateral difference.

Another "angle".........If you, the officer, can't get a reading off the plate of a vehicle then you are told to aim at the headlight. Would an officer try to get the second vehicle with only the headlight, drivers side, and mistakenly sample the first car?

In the training I have received.....we have always been told to target the front licence plate, if no plate, front centre between headlights OR on occassion the rear plate.....NEVER anywhere else and NEVER a partial corner (ie corner headlight) that is just stupid and not being used properly.

I am not that hard up for tickets to start corner jabbing vehicles. There will be another vehicle come along if I wait long enough. I won't lose sleep over it as the vehicles are still travelling even when I'm home.

Hi Bear:

I like your new avatar. Must check donut specifications - diameter, glazing thickness, and, most important, freshness.

Ive never used a lidar.

I look at health products and products that can have an impact on health. I cant see how a lidar can measure the speed of car2. The angles are too tight.

Imax wrote:

Hi Bear:

I like your new avatar. Must check donut specifications - diameter, glazing thickness, and, most important, freshness.

Especially the freshness.....and as Homer would say....mmmm donuts!

Imax wrote:

I cant see how a lidar can measure the speed of car2. The angles are too tight.

Simply, if it's in too close to V1 then it can not be targeted.

Now having said that, has the officer watched these 2 vehicles over time and neither appear to be gaining or pulling away from the other....then going relatively the same speed(within 5km/hr of each other). Could stop the 2nd one for speeding OR even follow too close.

Hi Bear:

As possibly the only one with lidar experience on this board, have you ever clocked two cars, one at 500 m and the other directly behind at 570m, and then managed to stop both cars by yourself ? (without causing an accident )

Imax wrote:

Hi Bear:

As possibly the only one with lidar experience on this board, have you ever clocked two cars, one at 500 m and the other directly behind at 570m, and then managed to stop both cars by yourself ? (without causing an accident )

I can only remember one of those types of stops about 3yrs ago. I have clocked 2 vehicles before (in the 150-155km/hr range) and successfully stopped both. This was about 3yrs ago (pre 172 era) I still remember the one vehicle (unusual vehicle travelling that speed) but don't remember the distances.

The most I have stopped at once is 9 vehicles. Great big line of vehicles, so I took out the lead vehicle and the 8 others stopped ....all related and travelling together!! That was before the car-pool era!